Field of the Invention
The present invention relates to an electrophotographic image forming apparatus that is used in devices such as copiers and printers.
Description of the Related Art
Image forming apparatuses employing an electrophotographic system or the like form an image pattern for tone correction on an intermediate transfer belt, detect the density of the image pattern, and perform tone correction based on the detected density. The surface wears with usage of the intermediate transfer belt, and unevenness occurs in the reflectance of the surface. This unevenness may also increase due to multilayering of a surface coat of the intermediate transfer belt. Since such unevenness affects the detected density of the image pattern, the accuracy of tone correction may be lowered.
U.S. Pat. No. 6,658,221 proposes creating a profile by sampling light reflected from the surface of an intermediate transfer belt on which a toner image is not formed, throughout one turn of the intermediate transfer belt, and using the profile to correct the detected density (amount of reflected light) of the image pattern.
Using the invention of U.S. Pat. No. 6,658,221 enables tone correction to be performed with high accuracy. However, the profile data for five turns of the intermediate transfer belt needs to be obtained. Since the user cannot form images during this period, so-called downtime occurs. A storage device for storing one turn worth of profile data is also required.